4 redis.conf学习

conf文件主要分成如下几个模块：

下面是conf文件（3.2.11）的中文注释，涵盖了大部分配置：

# Redis configuration file example.
#
# Note that in order to read the configuration file, Redis must be
# started with the file path as first argument:
#
# ./redis-server /path/to/redis.conf

# Note on units: when memory size is needed, it is possible to specify
# it in the usual form of 1k 5GB 4M and so forth:
#
# 1k => 1000 bytes
# 1kb => 1024 bytes
# 1m => 1000000 bytes
# 1mb => 1024*1024 bytes
# 1g => 1000000000 bytes
# 1gb => 1024*1024*1024 bytes
#
# units are case insensitive so 1GB 1Gb 1gB are all the same.

################################## INCLUDES ###################################

#引入其他配置文件，比如当你有多个server，而有些配置是它们公用的，那么可以将这些配
#置写入到一个配置文件中，然后这些server再include这个配置文件
# include /path/to/local.conf
# include /path/to/other.conf

################################## NETWORK #####################################

# By default, if no "bind" configuration directive is specified, Redis listens
# for connections from all the network interfaces available on the server.
# It is possible to listen to just one or multiple selected interfaces using
# the "bind" configuration directive, followed by one or more IP addresses.
#
# Examples:
#
# bind 192.168.1.100 10.0.0.1
#默认情况下，redis监听server所有可用的网络接口，bind配置监听一个或多个接口。
#监听多个接口时用空格隔开，例如，bind 127.0.0.1 10.0.0.1
bind 127.0.0.1

#开启后禁止公网访问redis。
protected-mode yes

#指定redis server监听的端口号，默认是6379,0是不监听
port 6379

#确定了TCP连接中已完成队列（完成三次握手之后）的长度，此值不许不大于Linux系统定义
#的/proc/sys/net/core/somaxconn值，默认是511，而Linux默认参数值是128。当系统并发
#量大并且客户端速度缓慢的时候，可以将这两个参数一起参考设定
tcp-backlog 511

#指定UNIX socket路径来让redis支持监听本地连接
#unixsocket /tmp/redis.sock

#指定unix socket file的权限
# unixsocketperm 700

#当client闲置多少秒后关闭连接，0为关闭该功能
timeout 0

# 将周期性的使用SO_KEEPALIVE检测客户端是否还处于健康状态，避免服务器阻塞，单位是s
tcp-keepalive 300

################################# GENERAL #####################################

# 守护进程开关
daemonize no

# 可以通过upstart和systemd管理Redis守护进程，这个参数是和具体的操作系统相关的
supervised no

# 配置pid文件路径。当Redis以守护模式启动时，如果没有配置pidfile，pidfile默认值是#/var/run/redis.pid
pidfile /var/run/redis_6379.pid

# 日志级别
# debug (记录大量日志信息，适用于开发测试阶段)
# verbose (较多日志信息)
# notice (适量日志信息，用于生产环境)
# warning (仅记录重要、关键信息)
loglevel notice

# 指定log路径，为空时，为标准输出，守护进程运行时，输出到 /dev/null
logfile ""

# 设置数据库个数。默认的数据库是DB0，可以在每个连接上使用select <dbid>命令选择一个#不同的数据库
databases 16

################################ SNAPSHOTTING  ################################
#RDB自动触发条件，save m n，含义是m秒内至少有n个keys发生改变则保存一次
#   save ""

save 900 1
save 300 10
save 60 10000

# bgsave过程出现错误是否停止接受写操作
stop-writes-on-bgsave-error yes

# 是否压缩rdb
rdbcompression yes

# 指定rdb file name
dbfilename dump.rdb

# 指定redis 工作目录
dir ./

################################# REPLICATION #################################

# 设置本机为slave
# slaveof <masterip> <masterport>

# 当master设置了密码保护，slave服务连接master的密码.
# masterauth <master-password>

# slave与master断连的时候是否继续响应客户端的request
#
slave-serve-stale-data yes

# slave是否为只读
slave-read-only yes

# 复制同步策略: disk or socket.
#
repl-diskless-sync no

# When diskless replication is enabled, it is possible to configure the delay
# the server waits in order to spawn the child that transfers the RDB via socket
# to the slaves.
#
# This is important since once the transfer starts, it is not possible to serve
# new slaves arriving, that will be queued for the next RDB transfer, so the server
# waits a delay in order to let more slaves arrive.
#
# The delay is specified in seconds, and by default is 5 seconds. To disable
# it entirely just set it to 0 seconds and the transfer will start ASAP.
repl-diskless-sync-delay 5

# 指定slave定期ping master的周期
# repl-ping-slave-period 10

# master 批量数据传输时间或者ping回复持剑间隔
# repl-timeout 60

#指定向slave同步数据时，是否禁用socket的no_delay option。如果是yes，则tcp协议栈#会合并小包统一发送，节省带宽，但会增加数据同步到slave的时间；若为no，则不会延迟
#小包的发送时机，这样数据同步的延时会减少，但需要更大的带宽。
repl-disable-tcp-nodelay no

# slaves被断开连接时存放slave数据的buffer大小
# repl-backlog-size 1mb

# 当master和slave断连多少s之后，情况backlog，设成0时永不清空
# repl-backlog-ttl 3600

# master不能正常工作的时候，redis sentinel会选最高优先级（值最小）作为master
slave-priority 100

# 当健康slave小于该配置值，master就停止写
# min-slaves-to-write 3
#延迟小于该配置s的slave才认为是健康的
# min-slaves-max-lag 10
#
# Setting one or the other to 0 disables the feature.
#
# By default min-slaves-to-write is set to 0 (feature disabled) and
# min-slaves-max-lag is set to 10.

# A Redis master is able to list the address and port of the attached
# slaves in different ways. For example the "INFO replication" section
# offers this information, which is used, among other tools, by
# Redis Sentinel in order to discover slave instances.
# Another place where this info is available is in the output of the
# "ROLE" command of a masteer.
#
# The listed IP and address normally reported by a slave is obtained
# in the following way:
#
#   IP: The address is auto detected by checking the peer address
#   of the socket used by the slave to connect with the master.
#
#   Port: The port is communicated by the slave during the replication
#   handshake, and is normally the port that the slave is using to
#   list for connections.
#
# However when port forwarding or Network Address Translation (NAT) is
# used, the slave may be actually reachable via different IP and port
# pairs. The following two options can be used by a slave in order to
# report to its master a specific set of IP and port, so that both INFO
# and ROLE will report those values.
#
# There is no need to use both the options if you need to override just
# the port or the IP address.
#
# slave-announce-ip 5.5.5.5
# slave-announce-port 1234

################################## SECURITY ###################################

# 设置redis连接密码
# requirepass foobared

# 命令重命名。如果把某个命令重命名成空字符串就等于取消了这个命令
#
# rename-command CONFIG ""
#
# Please note that changing the name of commands that are logged into the
# AOF file or transmitted to slaves may cause problems.

################################### LIMITS ####################################

# 设置最大客户端连接数量，0为不限制
#
# maxclients 10000

#指定Redis最大内存限制，redis达到最大内存后，会先清理已到期或即将到期的key，
#
# maxmemory <bytes>

#内存达到maxmemory时，redis采用哪种策略来减少内存
# volatile-lru -> 利用LRU算法移除设置过过期时间的key(LRU:Least Recently Used)
# allkeys-lru -> 利用LRU算法移除所有key
# volatile-random -> 移除设置过过期时间的随机key
# allkeys-random -> 随机移除key
# volatile-ttl -> 移除即将过期的key
# noeviction -> 不移除任何key，只返回一个错误
# The default is:
#
# maxmemory-policy noeviction

# LRU and minimal TTL algorithms are not precise algorithms but approximated
# algorithms (in order to save memory), so you can tune it for speed or
# accuracy. For default Redis will check five keys and pick the one that was
# used less recently, you can change the sample size using the following
# configuration directive.
#
# The default of 5 produces good enough results. 10 Approximates very closely
# true LRU but costs a bit more CPU. 3 is very fast but not very accurate.
#
# maxmemory-samples 5

############################## APPEND ONLY MODE ###############################

#AOF开关.

appendonly no

# The name of the append only file (default: "appendonly.aof")

appendfilename "appendonly.aof"

# 硬盘同步策略

# appendfsync always
appendfsync everysec
# appendfsync no

# AOF策略设置为always或者everysec是，后台处理进程（后台保存或者AOF日志重写）会执行
#大量的I/O操作，在某些Linux配置中会阻止过长的fsync（）请求。为了捡回这个问题，可以
#设置这个参数为no

no-appendfsync-on-rewrite no

# 自动触发AOF重写的参数

auto-aof-rewrite-percentage 100
auto-aof-rewrite-min-size 64mb

# AOF不完整的时候，redis启动时否继续加载AOF。
#yes会正常启动；no拒绝启动，返回error，如果此时再想启动redis则需要在启动使用
#"redis-check-aof"工具来修复AOF
aof-load-truncated yes
################################ LUA SCRIPTING  ###############################

# Max execution time of a Lua script in milliseconds.
#
# If the maximum execution time is reached Redis will log that a script is
# still in execution after the maximum allowed time and will start to
# reply to queries with an error.
#
# When a long running script exceeds the maximum execution time only the
# SCRIPT KILL and SHUTDOWN NOSAVE commands are available. The first can be
# used to stop a script that did not yet called write commands. The second
# is the only way to shut down the server in the case a write command was
# already issued by the script but the user doesn't want to wait for the natural
# termination of the script.
#
# Set it to 0 or a negative value for unlimited execution without warnings.
lua-time-limit 5000

################################ REDIS CLUSTER  ###############################
#是否enable集群
# cluster-enabled yes

# 设置集群配置文件名
# cluster-config-file nodes-6379.conf

# 节点相互连接的超时时间
# cluster-node-timeout 15000

# 在failover的时候，全部slave都会请求申请为master，但是有些slave可能与master断开连接
#一段时间了，导致数据过于陈旧，这样的slave不应该提升为master。
#该参数用来判断slave与master断连的时间是否过长。
#
#判断方法是:bijiao slave断连的时间和（node-timeout*slave-validity-factor）+repl-ping-slave-period
#如果节点超时时间设置为30s，并且cluster-slave-validity-factor为10s，假设默认的repl-ping-slave-period
#是10s，即如果超时310s slave将不会尝试进行failover。
#如果设置成0，则无论从节点与主节点失联多久，从节点都会尝试升级为master
# cluster-slave-validity-factor 10

# master需要的最小slave数，只有达到这个数，master失败时，它的从节点才会进行failover
#
# cluster-migration-barrier 1

# 当一定比例的键空间没有覆盖到（就是某一部分的哈希槽没了，有可能是暂时挂断了），集群就停止处理任何
#查询操作。如果该项设置为no，那么就算请求中只有一部分的key可以被查到，一样可以查询（但是有可能不全）
# cluster-require-full-coverage yes

# In order to setup your cluster make sure to read the documentation
# available at http://redis.io web site.

################################## SLOW LOG ###################################

# 执行时间比该值大的请求记录到slowlog里，单位是us。如果<0,会禁用slowlog,0则强制记录所有命令
slowlog-max-len 128

################################ LATENCY MONITOR ##############################

# 延迟监控功能，用来监控redis中执行比较慢的一些操作，用LATENCY打印redis实例在
#跑命令时的好事图表。只记录>=该配置的操作。0的话就是关闭监视
latency-monitor-threshold 0

############################# EVENT NOTIFICATION ##############################

# Redis can notify Pub/Sub clients about events happening in the key space.
# This feature is documented at http://redis.io/topics/notifications
#
# For instance if keyspace events notification is enabled, and a client
# performs a DEL operation on key "foo" stored in the Database 0, two
# messages will be published via Pub/Sub:
#
# PUBLISH [email protected]__:foo del
# PUBLISH [email protected]__:del foo
#
# It is possible to select the events that Redis will notify among a set
# of classes. Every class is identified by a single character:
#
#  K     Keyspace events, published with [email protected]<db>__ prefix.
#  E     Keyevent events, published with [email protected]<db>__ prefix.
#  g     Generic commands (non-type specific) like DEL, EXPIRE, RENAME, ...
#  $     String commands
#  l     List commands
#  s     Set commands
#  h     Hash commands
#  z     Sorted set commands
#  x     Expired events (events generated every time a key expires)
#  e     Evicted events (events generated when a key is evicted for maxmemory)
#  A     Alias for g$lshzxe, so that the "AKE" string means all the events.
#
#  The "notify-keyspace-events" takes as argument a string that is composed
#  of zero or multiple characters. The empty string means that notifications
#  are disabled.
#
#  Example: to enable list and generic events, from the point of view of the
#           event name, use:
#
#  notify-keyspace-events Elg
#
#  Example 2: to get the stream of the expired keys subscribing to channel
#             name [email protected]__:expired use:
#
#  notify-keyspace-events Ex
#
#  By default all notifications are disabled because most users don't need
#  this feature and the feature has some overhead. Note that if you don't
#  specify at least one of K or E, no events will be delivered.
# 是否发送键空间的改变的事件
notify-keyspace-events ""

############################### ADVANCED CONFIG ###############################

# hash数据类型使用ziplist编码的阈值
hash-max-ziplist-entries 512
hash-max-ziplist-value 64

# Lists are also encoded in a special way to save a lot of space.
# The number of entries allowed per internal list node can be specified
# as a fixed maximum size or a maximum number of elements.
# For a fixed maximum size, use -5 through -1, meaning:
# -5: max size: 64 Kb  <-- not recommended for normal workloads
# -4: max size: 32 Kb  <-- not recommended
# -3: max size: 16 Kb  <-- probably not recommended
# -2: max size: 8 Kb   <-- good
# -1: max size: 4 Kb   <-- good
# Positive numbers mean store up to _exactly_ that number of elements
# per list node.
# The highest performing option is usually -2 (8 Kb size) or -1 (4 Kb size),
# but if your use case is unique, adjust the settings as necessary.
#list使用ziplist编码的阈值
list-max-ziplist-size -2

# Lists may also be compressed.
# Compress depth is the number of quicklist ziplist nodes from *each* side of
# the list to *exclude* from compression.  The head and tail of the list
# are always uncompressed for fast push/pop operations.  Settings are:
# 0: disable all list compression
# 1: depth 1 means "don't start compressing until after 1 node into the list,
#    going from either the head or tail"
#    So: [head]->node->node->...->node->[tail]
#    [head], [tail] will always be uncompressed; inner nodes will compress.
# 2: [head]->[next]->node->node->...->node->[prev]->[tail]
#    2 here means: don't compress head or head->next or tail->prev or tail,
#    but compress all nodes between them.
# 3: [head]->[next]->[next]->node->node->...->node->[prev]->[prev]->[tail]
# etc.
#list压缩策略
list-compress-depth 0

#se使用intset编码的条件
set-max-intset-entries 512

# zet用ziplist编码的条件
zset-max-ziplist-entries 128
zset-max-ziplist-value 64

# HyperLogLog sparse representation bytes limit. The limit includes the
# 16 bytes header. When an HyperLogLog using the sparse representation crosses
# this limit, it is converted into the dense representation.
#
# A value greater than 16000 is totally useless, since at that point the
# dense representation is more memory efficient.
#
# The suggested value is ~ 3000 in order to have the benefits of
# the space efficient encoding without slowing down too much PFADD,
# which is O(N) with the sparse encoding. The value can be raised to
# ~ 10000 when CPU is not a concern, but space is, and the data set is
# composed of many HyperLogLogs with cardinality in the 0 - 15000 range.
#hyperloglog的值长度小于等于该值的时候用稀疏数据结构（sparse），否则用稠密（dense）
#的数据结构
hll-sparse-max-bytes 3000

# 是否开启rehash，hash扩容
activerehashing yes

# The client output buffer limits can be used to force disconnection of clients
# that are not reading data from the server fast enough for some reason (a
# common reason is that a Pub/Sub client can't consume messages as fast as the
# publisher can produce them).
#
# The limit can be set differently for the three different classes of clients:
#
# normal -> normal clients including MONITOR clients
# slave  -> slave clients
# pubsub -> clients subscribed to at least one pubsub channel or pattern
#
# The syntax of every client-output-buffer-limit directive is the following:
#
# client-output-buffer-limit <class> <hard limit> <soft limit> <soft seconds>
#
# A client is immediately disconnected once the hard limit is reached, or if
# the soft limit is reached and remains reached for the specified number of
# seconds (continuously).
# So for instance if the hard limit is 32 megabytes and the soft limit is
# 16 megabytes / 10 seconds, the client will get disconnected immediately
# if the size of the output buffers reach 32 megabytes, but will also get
# disconnected if the client reaches 16 megabytes and continuously overcomes
# the limit for 10 seconds.
#
# By default normal clients are not limited because they don't receive data
# without asking (in a push way), but just after a request, so only
# asynchronous clients may create a scenario where data is requested faster
# than it can read.
#
# Instead there is a default limit for pubsub and slave clients, since
# subscribers and slaves receive data in a push fashion.
#
# Both the hard or the soft limit can be disabled by setting them to zero.
#限制分配缓冲区的大小，防止内存无节制的分配
client-output-buffer-limit normal 0 0 0
client-output-buffer-limit slave 256mb 64mb 60
client-output-buffer-limit pubsub 32mb 8mb 60

# redis执行任务的频率为1s除以hz。当redis空闲时，提高该值将使用更多的cpu，但同时，
#当有许多**同时到期时，将使redis响应更敏捷，而超时可以更精确地处理。
hz 10

# AOF重写的时候，如果打开该开关，系统会每32MB执行一次fsync。可以避免过大的延迟峰值
aof-rewrite-incremental-fsync yes